NOAA National Weather Service alerts, predicts, and forecasts climate changes in the United States. This is a Ruby client library for NOAA created by developer Andrew M. Whalen. It contains data to interact with forecast and current weather conditions.
Before there was a Google Maps API, Adrian Holovaty created Chicago Crime to show updated crime data by location. Holovaty's lessons were later put into play in the Knight Foundation-funded EveryBlock, now owned by MSNBC. And now, EveryBlock has an API.
Genability, an energy data firm that enables new energy companies such as solar developers and EV manufacturers to integrate smart energy solutions into their products and services, recently announced an initiative that will distribute solar savings data, via an API, to consumers and players in the solar energy market.